Sao Tome and Principe was discovered and colonized by Portugal in the late 15th century. The Portuguese started with the use of slave labor to grow sugar on the islands and in the mid 1500´s it was Africas foremost exporter of sugar. In the 19th century sugar was replaced by cacao and coffee plantations(rocas) owned by large Portuguese companies and by 1908 Sao Tome had become the worlds largest producer of cacao which still is the countrys most important crop.
Even if Portugal officially abolished slavery in 1876, the rocas system continued to abuse workforce well into the 20th century. This led to an outbreak of riots in 1953 "the Batepa Massacre", where many workers were killed in clash with their Portuguese rulers.
When the Portuguese dictator Marcello Caetano was overthrown in the Carnation revolution in 1974, Portugal was committed to dissolve its overseas colonies and the São Toméan party MLSTP (Movement for the Liberation of Sao Tome and Principe) negotiated with the Portuguese authority and worked out an agreement for the transfer of sovereignty. São Tomé and Principe achieved independence on July 12, 1975.
In 1991 São Tomé and Principe held its first multi party election and have held regularly and fair elections ever since.